System for treating wastewater

ABSTRACT

A wastewater treatment system treating excess wastewater from a sewer system includes a generally vertically oriented first shaft structure adapted to receive excess wastewater from the sewer system, a generally vertically oriented second shaft structure spaced apart from the first shaft structure, a connector passage extending between the shaft structures proximate lower ends of the shaft structures, and an effluent passage in fluid communication with the second shaft structure. The treatment system further includes a treating agent dispenser for introducing a treating agent into the wastewater to disinfect at least a portion of the wastewater. During a sufficient rain event, the wastewater flows from the sewer system into the first shaft structure, then through the connector passage and the second shaft structure, and into the effluent passage, such that flow time through the shaft structures is greater than flow time through the connector passage.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to systems and methods for treating excesswastewater from a sewer system, such as a combined sewer system or asanitary sewer system.

2. Background Art

A combined sewer system is a sewer system that is designed to carry bothsanitary sewage and storm water runoff. Such sanitary sewage and/orstorm water runoff may be referred to as wastewater. During normalconditions, such as dry weather conditions, wastewater is transported bythe combined sewer system to a wastewater treatment facility, where thewastewater is treated prior to being discharged. During a rain event,however, flow of wastewater may exceed treatment capacity of thetreatment facility. In such a case, overflow wastewater may be divertedto one or more storage basins or tunnels until the treatment facility isable to treat the excess wastewater.

SUMMARY OF THE INVENTION

Under the invention, a wastewater treatment system is provided fortreating excess wastewater from a sewer system. The treatment systemincludes a generally vertically oriented first shaft structure adaptedto receive excess wastewater from the sewer system, a generallyvertically oriented second shaft structure spaced apart from the firstshaft structure, a connector passage extending between the shaftstructures proximate lower ends of the shaft structures, and an effluentpassage in fluid communication with the second shaft structure. Thetreatment system further includes a treating agent dispenser forintroducing a treating agent into the wastewater. During a sufficientrain event, the wastewater flows from the sewer system into the firstshaft structure, then through the connector passage and the second shaftstructure, and into the effluent passage, such that flow time throughthe shaft structures is greater than flow time through the connectorpassage. Furthermore, the treating agent dispenser is operative tointroduce the treating agent to thereby disinfect at least a portion ofthe wastewater.

Further under the invention, a method for treating excess wastewaterfrom a sewer system is provided. The method includes the steps ofreceiving the excess wastewater from the sewer system in a generallyvertically oriented first shaft structure; allowing the wastewater toflow generally in a first direction through the first shaft structure,then through a connector passage in fluid communication with the firstshaft structure, and then generally in a second direction through agenerally vertically oriented second shaft structure spaced away fromthe first shaft structure, wherein the second direction is differentthan the first direction; introducing a treating agent into thewastewater so as to disinfect at least a portion of the wastewater; andallowing a portion of the wastewater to flow from the second shaftstructure to an effluent passage in fluid communication with the secondshaft structure after the step of introducing the treating agent;wherein flow time through the shaft structures is greater than flow timethrough the connector passage.

Still further under the invention, a wastewater receiving system forreceiving excess wastewater from a sewer system is provided. Thewastewater receiving system includes a generally vertically orientedshaft structure adapted to receive excess wastewater from the sewersystem, and an effluent passage in fluid communication with the shaftstructure. The shaft structure has a hydraulic diameter and a heightgreater than at least fifty percent of the hydraulic diameter. During asufficient rain event, the excess wastewater flows from the sewer systeminto the shaft structure such that when the shaft structure reaches apredetermined fill level, the wastewater flows across the shaftstructure and into the effluent passage.

While exemplary embodiments in accordance with the invention areillustrated and disclosed, such disclosure should not be construed tolimit the claims. It is anticipated that various modifications andalternative designs may be made without departing from the scope of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a treatment system according to theinvention in fluid communication with a sewer system, wherein thetreatment system includes first and second shaft structures connectedtogether by a connector passage;

FIG. 2 is a horizontal cross-sectional view of the first and secondshaft structures represented in the schematic view of FIG. 1, takenalong a line similar to line 2-2 shown in FIG. 1;

FIG. 3 is a schematic view of the treatment system during a rain eventshowing excess wastewater flowing from the sewer system into the shaftstructures;

FIG. 4 is a schematic view of the treatment system showing excesswastewater passing from the second shaft structure to an effluentpassage in fluid communication with the second shaft structure;

FIG. 5 is a schematic view of the treatment system after the rain eventhas subsided, and showing the shaft structures being dewatered; and

FIG. 6 is a schematic view of a wastewater storage system including asingle shaft structure.

DETAILED DESCRIPTION

FIGS. 1-5 show a wastewater treatment system 10 according to theinvention for treating excess wastewater from a sewer system 12. Sewersystem 12 may be, for example, a combined sewer that is designed tocarry both sanitary sewage and storm water runoff (combined seweroverflow), or a sanitary sewer system that experiences increased flowsduring a rain event (sanitary sewer overflow). Such a sanitary sewersystem may experience increased flows due to storm water infiltrationinto the sanitary sewer system. The term “wastewater” as used in theapplication refers to sanitary sewage and/or storm water runoff.

The wastewater treatment system 10 includes a diversion chamber 13 andan influent passage 14 for receiving excess wastewater, such aswastewater overflow, from the sewer system 12. The treatment system 10further includes a container having first and second spaced apartportions, such as first and second shaft structures 15 and 16,respectively, in fluid communication with the influent passage 14, andconnected together by a connector passage 17.

In one embodiment of the invention, the shaft structures 15 and 16 aredisposed substantially or entirely below ground and are orientedgenerally vertically. For example, each shaft structure 15 and 16 mayhave a longitudinal axis that is coincident with a vertical line or thatextends at an angle with respect to a vertical line. While the shaftstructures 15 and 16 may have any suitable configuration, in oneembodiment of the invention, each shaft structure 15 and 16 has agenerally circular horizontal cross-section having a diameter in therange of 10 to 200 feet. Alternatively, each shaft structure 15 and 16may have a cross-section that defines any suitable shape, such as ahexagon, octagon, ellipse, or rectangle, and that has any suitablehydraulic diameter, such as a hydraulic diameter in the range of 5 to200 feet. In addition, each shaft structure 15 and 16 may have anysuitable length, such as a generally vertical length in the range of 30to 200 feet.

The shaft structures 15 and 16 may have generally the same size andshape. Alternatively, the shaft structures 15 and 16 may have differentsizes and/or shapes. For example, the first shaft structure 15 may havea smaller hydraulic diameter than the second shaft structure 16. As amore detailed example, the first shaft structure 15 may have a hydraulicdiameter in the range of 5 to 40 feet, and the second shaft structure 16may have a hydraulic diameter in the range of 20 to 200 feet.

Furthermore, each shaft structure 15 and 16 may be made of concrete,and/or any other suitable material such as steel. For example, eachshaft structure 15 and 16 may comprise a plurality of concrete ringsthat are stacked on top of each other in a sealed relationship.

The connector passage 17 may extend generally horizontally, and may beconnected to each shaft structure 15 and 16 proximate a lower end ofeach shaft structure 15 and 16. Furthermore, the connector passage 17may have any suitable configuration for allowing wastewater to flowbetween the shaft structures 15 and 16. For example, the connectorpassage 17 may be a generally cylindrical structure having across-section that defines any suitable shape, such as a circle,hexagon, octagon, ellipse, or rectangle. The connector passage 17 mayalso have any suitable hydraulic diameter, such as a hydraulic diameterin the range of 5 to 30 feet, and any suitable length, such as a lengthin the range of 1 to 500 feet. Moreover, the connector passage 17 maycomprise concrete and/or any other suitable material, such as steel.

With the above configuration, the volume defined by each shaft structure15 and 16 may be greater than the volume defined by the connectorpassage. For example, the volume defined by each shaft structure 15 and16 may be at least double the volume defined by the connector passage17.

The treatment system 10 also includes a treating agent dispenser, suchas a treating agent injection system 18, for injecting or otherwiseintroducing a treating agent, such as chlorine or a solution thatincludes chlorine, into the excess wastewater so as to treat the excesswastewater. For example, the treating agent may be a sodium hypochloritedisinfection solution that is used to disinfect the excess wastewater.The treating agent injection system 18 may also include a mixer (notshown) disposed at or near the point of injection for mixing thetreating agent with the excess wastewater. The mixer may include, forexample, a bubbler and/or a mechanical mixer.

The treatment system 10 may also include a computer control system, suchas a controller 20, in communication with the treating agent injectionsystem 18 for controlling introduction of the treating agent. Thecontroller 20 may also be in communication with a flow sensor 22disposed in the influent passage 14.

While the treating agent injection system 18 and controller 20 may eachbe disposed in any suitable position, in the embodiment shown in FIG. 1,the treating agent injection system 18 is located proximate the influentpassage 14 and the controller 20 is disposed proximate the second shaftstructure 16. As another example, the treating agent injection system 18and controller 20 may each be disposed proximate, such as on top of,either shaft structure 15 or 16. Furthermore, the treating agentinjection system 18 and 20 may be housed in the same or separatestructures or enclosures.

An effluent passage 24 is in fluid communication with the second shaftstructure 16. The effluent passage 24 may be used to discharge treatedwastewater from the treatment system 10 to a river 26 or any othersuitable area, such as another receiving water body.

Referring to FIGS. 1-5, operation of the treatment system 10 will now bedescribed in detail. Under normal operating conditions, such as duringdry weather conditions, wastewater flows through trunk sewer 28 of thesewer system 12 and into an interceptor 30 as shown in FIG. 1. Theinterceptor 30 carries wastewater to a treatment facility, such as awastewater treatment plant (not shown). During a sufficient rain event,flow from the trunk sewer 28 will exceed capacity of the interceptor 30,and excess wastewater will flow into influent passage 14. As shown inFIG. 3, for example, excess wastewater may flow over a weir 32 indiversion chamber 13 and into influent passage 14. Advantageously, thetreatment system 10 may be configured to handle a relatively large flowrate, such as a flow rate in the range of 2,000 to 1,500,000 gallons perminute.

When flow is detected by the flow sensor 22, for example, the controller20 may cause the treating agent injection system 18 to initiateinjection of the treating agent into the excess wastewater. The treatingagent may be injected at any suitable rate, such as a rate sufficient toachieve a treating agent level in the range of 10 to 25 milligrams perliter of excess wastewater, for example. Mixers of the treating agentinjection system 20 may also be used to enhance mixing of the treatingagent with the excess wastewater. Such mixers may be located, forexample, at and/or downstream of the point of treating agent injection.

Alternatively, treating agent injection may begin at any suitable time,such as immediately upon flow exceeding capacity of the interceptor 30,or any time thereafter, such is when flow is detected in one or both ofthe shaft structures 15 and 16. Furthermore, treating agent injectionmay occur at any suitable point, such as upstream of the shaftstructures 15 and 16, within one or both of the shaft structures 15 and16, and/or within the connector passage 17. For example, treating agentinjection may occur upstream of the weir 32 to facilitate mixing of thetreating agent with the excess wastewater.

After flowing over the weir 32, excess wastewater may then flow throughone or more screens 34, such as inclined, vertical and/or horizontalscreens, located in the influent passage 14 and/or first shaft structure15 so as to remove floatable matter and/or suspended solids from theexcess wastewater. Excess wastewater may then flow generally in a firstdirection, such as downward, in the first shaft structure 15, throughthe connector passage 17 and then generally in a second direction, suchas upward, in the second shaft structure 16.

If the rain event continues, excess wastewater will flow through thefirst shaft structure 15, through the connector passage 17 and into thesecond shaft structure 16 until the second shaft structure 16 reachescapacity. Eventually, if the rain event continues, treated excesswastewater will flow into the effluent passage 24 and then into theriver 26, as shown in FIG. 4. The treatment system 10 may include one ormore screens 36, such as inclined, vertical and/or horizontal screens,disposed in the second shaft structure 16, and/or one or more screens38, such as inclined, vertical and/or horizontal screens, disposed inthe effluent passage 24 for removing floatables and/or suspended solidsfrom the treated excess wastewater. Such screens 36 and/or 38 may beprovided as an alternative to or in addition to the screens 34 locatedin the influent passage 14 and/or first shaft structure 15.

The treatment system 10 is configured to enable sufficient contact timeto occur between the treating agent and the excess wastewater as theexcess wastewater continuously flows from the point of treating agentinjection to the point of discharge from the effluent passage 24, so asto achieve sufficient disinfection, e.g., bacteria kill, of the excesswastewater at the point of discharge. Sufficient disinfection may beachieved, for example, when the mean fecal coliform bacteria level isless than 400 counts per 100 milliliters of excess wastewater, or othersuitable level.

In one embodiment of the invention, the treatment system 10 may beconfigured to provide a total contact time in the range of 10 to 30minutes, which may include contact time that occurs in sewer system 12,the influent passage 14, the shaft structures 15 and 16, the connectorpassage 17 and/or the effluent passage 24. Alternatively, the treatmentsystem 10 may be configured to provide any suitable contact time, suchas a contact time of less than 10 minutes or greater than 30 minutes, soas to achieve a desired disinfection level.

A majority of the contact time, if not all of the contact time, may beprovided by the shaft structures 15 and 16 and connector passage 17.Furthermore, in contrast to a prior system having a generally horizontalflow through tunnel where the majority of contact time is provided inthe tunnel as compared to corresponding drop and riser shafts, the shaftstructures 15 and 16 of the treatment system 10 may be configured toprovide a majority of the contact time as compared to the connectorpassage 17. For example, the flow time through the shaft structures 15and 16 may be at least double the flow time through the connectorpassage 17. As another example, flow time through each shaft structure15 and 16 may be at least double the flow time through the connectorpassage 17.

With the connector passage 17 disposed proximate lower ends of the shaftstructures 15 and 16, excess wastewater may flow generally downwardlythrough the first shaft structure 15, and then generally upwardlythrough the second shaft structure 16 after passing through theconnector passage 17. In one embodiment of the invention, the secondshaft structure 16 may be configured to provide an upward flow rate inthe range of 0.05 to 1.0 feet per second, for a flow rate into theinfluent passage 14 in the range of 2,000 to 1,500,000 gallons perminute.

As the excess wastewater flows through the first shaft structure 15,floatable matter that is not trapped by the screens 34 may remainproximate an upper end of the first shaft structure 15. Furthermore, asthe excess wastewater flows through shaft structures 15 and 16,relatively heavy solids not removed by the screens 34 and 36 may settleat the bottom of one or both of the shaft structures 15 and 16.

The treatment system 10 may also be configured to provide dechlorinationof the excess wastewater before discharging the excess wastewater to theriver 26, or other suitable area. For example, the treatment system 10may include a dechlorinating agent dispenser, such as a dechlorinatingagent injection system 39, for introducing a dechlorinating agent, suchas sulfate, into the effluent passage 24. The dechlorinating agentinjection system 39 may be controlled by the controller 20, or by othersuitable means, so that the dechlorinating agent will be introduced at asuitable point. Because dechlorination does not require much, if any,contact time, the dechlorinating agent may be introduced into theeffluent passage 24 proximate to the discharge point of the effluentpassage 24.

As the rain event subsides, the capacity of the interceptor 30 will nolonger be exceeded, and flow to the shaft structures 15 and 16 willcease. Dewatering of the shaft structures 15 and 16 may begin when theinterceptor 30, or other suitable passage, has the capacity to acceptdewatering flow rates. The dewatering process begins by disposing all ofthe matter that was collected by the screens 34-38 into one or both ofthe shaft structures 15 and 16. For example, collected matter may be maybe combed, brushed, or otherwise scraped from the screens 34-38.Alternatively, such matter may be removed from the screens 34-38 anddisposed of elsewhere. One or more submersible pumps 40, for example,may then be used to pump wastewater from shaft structures 15 and 16 to adewatering passage 41, such as one or more pipes, in fluid communicationwith the shaft structures 15 and 16. The dewatering passage 41 may beused to route wastewater from the shaft structures 15 and 16 to theinterceptor 30 and/or to another suitable passage so as to route theexcess wastewater to the wastewater treatment plant (not shown), forexample. In one embodiment, the dewatering passage 41 may extendgenerally upwardly in the second shaft structure 16, through a side wallof the second shaft structure 16, and to the interceptor 30.

In one embodiment of the invention, the second shaft structure 16 mayextend below the first shaft structure 15, and the connector passage 17may slope downwardly toward the second shaft structure 16 to facilitatedewatering of the shaft structures 15 and 16. As another example, thefirst shaft structure 15 may extend below the second shaft structure 16,and the connector passage 17 may slope downwardly toward the first shaftstructure 15 to facilitate dewatering of the shaft structures 15 and 16through a dewatering passage disposed in and/or connected directly tothe first shaft structure 15.

The treatment system 10 may also include a flushing system (not shown)for flushing one or both of the shaft structures 15 and 16 and/orconnector passage 17 to remove sludge, for example. Such a flushingsystem may have any suitable configuration, such as one or more sprayheads or nozzles mounted on one or more shaft side walls and connectedto a submersible pump. As another example, the flushing system mayinclude one or more tipping or dump buckets located above the high waterlevel of one or both of the shaft structures 15 and 16.

Because the shaft structures 15 and 16 may be configured to providerelatively small vertical flow velocities, head losses caused by theshaft structures 15 and 16 may be relatively small. For example, headlosses associated with the shaft structures 15 and 16 may be less than 3feet. As a result, head drop between the influent passage 14 and theeffluent passage 24 may be relatively small. Consequently, depending onflow rates and available head provided by the sewer system 12, thetreatment system 10 may operate as a gravity feed system, wherein excesswastewater may flow through the shaft structures 15 and 16 and out theeffluent passage 24 without requiring pumping. Furthermore, low flowvelocities through the shaft structures 15 and 16 also enable solids tosettle at the bottom of the shaft structures 15 and 16. Alternatively,the treatment system 10 may include one or more pumps 42 for pumpingexcess wastewater from the second shaft structure 16 into the effluentpassage 24, and/or one or more pumps (not shown) for pumping excesswastewater from the influent passage 14 into the first shaft structure15.

The treatment system 10 may further include an additional container,such as a storage tunnel, that is in inhibitable fluid communicationwith one or both of the shaft structures 15 and 16. For example, thetreatment system 10 may include a tunnel 44 (shown in phantom lines inFIG. 1) connected to the second shaft structure 16 at or near the lowerend of the second shaft structure 16. Such a tunnel may be used, forexample, to receive a first quantity of excess wastewater or “firstflush,” which may have a high percentage of total suspended solids. Whenexcess wastewater received in the tunnel 44 reaches a predeterminedlevel, flow to the tunnel 44 may be inhibited, such as by using anautomatic gate disposed proximate the junction of the tunnel 44 with thesecond shaft structure 16. As another example, flow into the tunnel 44may be inhibited when the tunnel 44 reaches capacity. When flow into thetunnel 44 is inhibited, wastewater may then flow from the first shaftstructure 15 to the second shaft structure 16, and then into theeffluent passage 24, as described above in detail. Further detailsregarding the use of such a tunnel are disclosed in U.S. Pat. No.6,503,404, which is hereby incorporated by reference in its entirety.

Moreover, the treatment system 10 may include more than two spaced apartshaft structures for further increasing flow time and/or contact time.For example, the treatment system 10 may include third and fourth shaftstructures (not shown) located proximate the shaft structures 15 and 16.The third shaft structure may be connected to the second shaft structure16 with a connector passage located proximate upper ends of the secondshaft structure 16 and third shaft structure. Likewise, the fourth shaftstructure may be connected to the third shaft structure with a connectorpassage located proximate lower ends of the third and fourth shaftstructures.

As another example, a divided shaft structure, such as disclosed in U.S.Pat. No. 6,503,404, may be used in conjunction with the shaft structures15 and 16. More specifically, such a divided shaft structure may beconnected upstream of the first shaft structure 15, and/or downstream ofthe second shaft structure.

FIG. 6 shows a wastewater storage or receiving system 50, according toanother aspect of the invention, for receiving excess wastewater from asewer system, such as sewer system 12 described above, through aninfluent passage 52. The system 50 includes a generally verticallyoriented shaft structure 54 adapted to receive excess wastewater fromthe sewer system, and an effluent passage 56 in fluid communication withthe shaft structure 54.

In this embodiment, treating agent, such as described above, may beadded to the excess wastewater upstream of the shaft structure 54 asufficient distance to achieve necessary contact time prior to thewastewater reaching the shaft structure 54. The treating agent may beinjected or otherwise introduced to the wastewater by a treating agentdispenser 18′.

The shaft structure 54 is configured to receive wastewater, such aspretreated wastewater, in relatively large quantities, such as 500,000gallons to 20,000,000 gallons or more. As another example, the shaftstructure 54 may be configured to receive less than 500,000 gallons ofwastewater. Furthermore, the shaft structure 54 is configured to allowtreated wastewater to be discharged through the effluent passage 56 to ariver 57 or any other suitable area, such as another receiving waterbody, when the wastewater received by the shaft structure 54 reaches apredetermined level.

The shaft structure 54 may have a cross-section that defines anysuitable shape, such as a circle, hexagon, octagon, ellipse, orrectangle. Furthermore, the shaft structure 54 may have any suitablehydraulic diameter D and a height H (measured from the bottom of theshaft structure 54 to the bottom of the effluent passage 56 at thejunction of the effluent passage 56 with the shaft structure 54) that isgreater than at least 50% of the hydraulic diameter D. For example, thehydraulic diameter D may be in the range of 30 to 200 feet, and theheight H may be in the range of 50 to 200 feet. In one embodiment, theheight H is at least 70% of the hydraulic diameter D, and in anotherembodiment, the height H is at least 110% of the hydraulic diameter D.

During a sufficient rain event, excess wastewater flows from the sewersystem through the influent passage 52 and into the shaft structure 54,such that when the shaft structure 54 reaches a predetermined filllevel, the wastewater flows across the shaft structure 54 and into theeffluent passage 56. The system 50 may also include one or more screens58 for filtering the wastewater prior to being discharged.

After the rain event has subsided, the shaft structure 54 may bedewatered in a similar manner as described above with respect to thesystem 10. For example, the wasterwater contained in the shaft structure54 may be pumped to the sewer system 12 using one or more submersiblepumps 40′ connected to dewatering passage 41′. Furthermore, the shaftstructure 54 may be flushed in a similar manner as described above withrespect to the system 10.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. A wastewater treatment system for treating excess wastewater from asewer system, the wastewater treatment system comprising: a generallyvertically oriented first shaft structure adapted to receive excesswastewater from the sewer system; a generally vertically oriented secondshaft structure spaced apart from the first shaft structure; a connectorpassage extending between the shaft structures proximate lower ends ofthe shaft structures; an effluent passage in fluid communication withthe second shaft structure; and a treating agent dispenser forintroducing a treating agent into the wastewater; wherein during asufficient rain event, the wastewater flows from the sewer system intothe first shaft structure, then through the connector passage and thesecond shaft structure, and into the effluent passage, such that flowtime through the shaft structures is greater than flow time through theconnector passage, and wherein the treating agent dispenser is operativeto introduce the treating agent to thereby sufficiently disinfect atleast a portion of the wastewater.
 2. The system of claim 1 wherein theconnector passage defines a volume, and each shaft structure defines ashaft volume that is greater than the volume of the connector passage.3. The system of claim 1 wherein the connector passage has a length inthe range of 1 to 500 feet, and each shaft structure has a hydraulicdiameter in the range of 5 to 200 feet.
 4. The system of claim 1 whereinthe first shaft structure has a first hydraulic diameter, and the secondshaft structure has a second hydraulic diameter that is greater than thefirst hydraulic diameter.
 5. The system of claim 1 wherein the firstshaft structure has a first hydraulic diameter in the range of 5 to 40feet, and the second shaft structure has a second hydraulic diameterthat is in the range of 20 to 200 feet.
 6. The system of claim 1 whereinthe flow time through the shaft structures is at least double the flowtime through the connector passage.
 7. The system of claim 1 wherein theflow time through each shaft structure is at least double the flow timethrough the connector passage.
 8. The system of claim 1 wherein theshaft structures are configured to accommodate a flow rate of at least2,000 gallons per minute.
 9. The system of claim 1 wherein the treatingagent dispenser is configured to introduce the treating agent upstreamof the first shaft structure.
 10. The system of claim 1 wherein thetreating agent dispenser is configured to introduce the treating agentwithin at least one of the shaft structures.
 11. The system of claim 1wherein the shaft structures are disposed substantially below groundlevel and are configured such that wastewater is able to flow throughthe shaft structures and to the effluent passage without requiringpumping, and wherein head loss associated with the shaft structures isless than three feet.
 12. (canceled)
 13. (canceled)
 14. (canceled) 15.(canceled)
 16. (canceled)
 17. (canceled)
 18. (canceled)
 19. (canceled)20. (canceled)
 21. (canceled)
 22. The system of claim 1 wherein duringthe sufficient rain event, the wastewater flows generally downwardthrough the first shaft structure and generally upward through thesecond shaft structure.
 23. The system of claim 22 wherein the secondshaft structure is configured such that upward flow rate in the secondshaft structure is in the range of 0.05 to 1 feet per second for a flowrate into the first shaft structure of 2,000 to 1,500,000 gallons perminute.
 24. The system of claim 1 wherein during a sufficient rainevent, the system is configured such that wastewater flows continuouslyfrom the first shaft structure, through the connector passage, and thenfrom the connector passage to the second shaft structure.
 25. The systemof claim 1 wherein the effluent passage is configured to dischargetreated wastewater to a body of water.
 26. The system of claim 1 whereinthe connector passage has a length in the range of 1 to 500 feet, andeach shaft structure has a hydraulic diameter in the range of 5 to 200feet.
 27. The system of claim 1 wherein the first shaft structure has afirst hydraulic diameter in the range of 5 to 40 feet, and the secondshaft structure has a second hydraulic diameter that is in the range of20 to 200 feet.
 28. The system of claim 1 wherein the shaft structuresare disposed substantially below ground level and are configured suchthat wastewater is able to flow through the shaft structures and to theeffluent passage without requiring pumping, and wherein head lossassociated with the shaft structures is less than three feet.